The present disclosure relates generally to welding systems, and more particularly to a reciprocating wire feed system configured to enable controlled short circuits between a welding wire and an advancing weld.
A wide range of welding systems and welding control regimes have been implemented for various purposes. In continuous welding processes with consumable electrode, gas metal arc welding (GMAW), and more specifically, metal inert gas (MIG) or metal active gas (MAG) techniques (collectively called GMAW) allow for formation of a continuing weld bead by feeding welding wire electrode shielded by gas (typically an inert gas or gas containing inert agents or active gas such as CO2 or oxygen) from a welding torch. One variation of GMAW is Flux Cored Arc Welding (FCAW) with a consumable electrode containing flux in the core surrounded by metal sheath. In such applications, the welding can be done with or without shielding gas. Another welding process is submerged arc welding (SAW), or sub-arc for short, where shielding is accomplished by solid powder flux instead of gas, and the arc is buried under the flux bed. Another welding process decouples wire feed from the heat source, where the heat source may be laser, electron beam, plasma or TIG, and the wire (e.g., consumable electrode) may be cold or “hot” (e.g., pre-heated) before entering (e.g., being deposited) into the melted puddle on the workpiece created by the heat source. Electrical power is applied to the welding wire and a circuit is completed through the workpiece to sustain an arc that melts the wire and the workpiece to form the desired weld.
Advanced forms of welding with consumable electrode can be based upon controlled short circuits between the wire electrode and the advancing weld puddle formed from melted metal of the workpieces and the wire electrode. One method of controlling short circuit behavior is welding current reduction during short-to-arc and arc-to-short transitions via current regulation or a secondary switch in the welding power supply.
In other applications, the controlled short circuits may be created by a reciprocating wire feed system configured to oscillating the welding wire in and out of the advancing weld puddle. By oscillating the wire in and out of the weld puddle, liquid at the end of the welding wire may be dipped into the puddle mechanically and detached form the welding wire when the wire is pulled out of the puddle, thereby accomplishing a “controlled short circuit” effect. Typically, mechanical motion of the wire is slow. To achieve desired higher deposition and faster welding travel speed, the wire must move bi-directionally in excess of 1000 inches per minute and at a rate in excess of 100 Hz at 100% duty cycle. Traditional reciprocating wire feed systems use a bi-directional motor, and bi-directional motors typically have high torque requirements to overcome the inertia of the motor, the drive rolls and/or gears. Bi-directional motors may have limitations on the reciprocating frequency (which in turn imposes limitation on wire feed and travel speeds and productivity), and may be susceptible to overheating, and/or may be oversized, which may cause weld joint accessibility issues.